A rotary compressor in which a plurality of cylinder chambers are formed in a compression mechanism by providing an annular piston in an annular cylinder chamber of a cylinder has been proposed (see, e.g., Japanese Patent Publication Nos. 2007-113493 and 2006-307762). A compressor of Japanese Patent Publication No. 2007-113493 has two cylinder chambers formed inside and outside an annular piston. A compressor of Japanese Patent Publication No. 2006-307762 has three cylinder chambers.
In general, cycle efficiency of a refrigeration cycle improves when the number of compression stages in a compression stroke is increased. Thus, the compressor of Patent Document 1 can be used to perform a two-stage compression refrigeration cycle, and the compressor of Patent Document 2 can be used to perform a three-stage compression refrigeration cycle.